74 



EVENINGS AT THE MICROSCOPE. 



DOUBLING AND HOOKS IX A BEE S WI>"G. 



seeming to be, as it were, cut out of the hinder and inner 

 side of the fore ones. The two edsres — the hinder edo-e of 



the fore pair and the 

 front edge of the hind 

 pair — then corre- 

 spond ; but it is neces- 

 sary that, during flight, 

 when the wings are ex- 

 panded, the two wings 

 on each side should 

 maintain this relative 

 position, neither over- 

 lapping the other, but 

 together presenting 

 one broad surface, 

 wherewith to beat the 

 air. There must be, therefore, some contrivance for 

 locking together the two edges in question, which yet 

 shall be capable of being unlocked at the pleasure of 

 the animal ; for the wings during repose slide over one 

 another. This contrivance is furnished by a series of 

 hairs or spines running along the front edge of the hind- 

 wing ; they are bent up into strong semicircular hooks, 

 arching outwards, looking, under a high power, like the 

 hooks on a butcher's stall. On the other hand, the margin 

 of the fore-wing is strengthened, and is turned-over with 

 a shallow doubling, so as to make a groove into which 

 the hooks catch ; and thus, while the fore-wings are ex- 

 panded, the hooks of the other pair are firmly locked in 

 their doubled edge ; while, as soon as flight ceases, and 

 the wings are relaxed, there is no hindrance to the 

 sliding of the fore over the hind pair. 



The wings of many insects are interesting on account 

 of the organs with which they are clothed. A familiar 

 example is furnished by the common Gnat, a wing of 

 which is on the slide now before us. There is the same 



